A liquid crystal display device includes a liquid crystal display panel, and a backlight unit that is disposed on a rear surface of the liquid crystal display panel, wherein the liquid crystal display panel adjusts penetration ratio (penetration amount) of light from the backlight unit and displays an image on a front surface of the liquid crystal display panel.
The backlight unit is roughly classified into two kinds. One is a light guide plate type (edge-light type) that outputs light from a side of the light guide plate, and the other is a direct type in which a light source is disposed on a rear surface of a liquid crystal module. In recent years, request for thickness reduction and side reduction of the liquid crystal display device is increasing, and more and more liquid crystal display devices are employing a backlight unit of the edge-light type that is advantageous to thickness reduction compared with the direct type.
A conventional backlight unit is described with reference to drawings. FIG. 7 is a front view of the conventional backlight unit that is used for a liquid crystal display device, and FIG. 8 is a sectional view taken along a VIII-VIII line of the backlight unit shown in FIG. 7. The backlight unit 92 is a light output device that outputs planar light from a rear surface of a liquid crystal display panel (not shown), and includes: a plurality of light sources 97; a plurality of light guide plates 95 that output light from the light source 97 as the planar light to the liquid crystal display panel; and a backlight chassis 94 in which the light source 97 and the light guide plate 95 are disposed. The backlight unit 92 includes a fixing clip 96 as well that fixes the light guide plates 95 ranged and disposed in a short-edge direction to the backlight chassis 94.
The light guide plate 95 is an elongated member formed of a transparent material that transmits light, and includes: a light reception portion 950 that receives the light from the light source 97; and an output portion 952 that outputs the light received by the light reception portion 950 as the planar light. In the light guide plate 95, an end surface in a long-edge direction defines the light reception portion 950, and a surface, which is adjacent to the light reception portion 950 and faces frontward, defines the output portion 952.
The light guide plate 95 includes, on a side opposite to the output portion 952, a fixing convex portion 951 that protrudes in the short-edge direction. When ranging the light guide plates 95 in the backlight chassis 94 in the short-edge direction, the fixing convex portions 951 of adjacent light guide plates 95 are disposed near to each other. The fixing clip 96 pushes the adjacent fixing convex portions 951 and engages with the backlight chassis 94, whereby the light guide plate 95 is ranged in the short-edge direction and fixed to the backlight chassis 94.
The backlight unit 92 includes the plurality of light guide plates 95 to be able to output the light, which has a different brightness for every one of the light guide plates 95, to the liquid crystal display panel (not shown) that is an illumination target. According to this, it is possible to raise contrast of an image displayed by the liquid crystal display panel and to improve display quality of a moving image.
In the liquid crystal display device, for example, there is a case where an image such as a white image or the like, which has an even brightness in a plane, is displayed. At this time, the backlight unit 92 is required to output the planar light that has the even brightness in the plane.
However, as shown in FIG. 8, in the backlight unit 92, a large gap is formed between the output portions 952 of the adjacent light guide plates 95, and there is a case where the light from the output portion 952 does not sufficiently extend into the gap. If the light does not extend into the gap between the output portions 952, the planar light output from the backlight unit 92 declines in brightness at the gap portion, and the brightness decline leads to brightness unevenness.
To avoid this, in the invention of JP-A-2004-273185, a light guide plate and a light emitting device are fixed to each other by means of a transparent adhesive to reduce a gap between the light emitting device and the light guide plate, whereby the brightness decline (i.e., brightness unevenness) of a plane-shaped illumination device (which corresponds to the backlight unit in the present invention) is alleviated. By bonding a plurality of light guide plates to one another by means of a transparent adhesive shown in JP-A-2004-273185, it is possible to reduce the gap between the output portions and remove the brightness unevenness.